The objective of this project is to characterize dose-response relationships and toxicity of tetrahydrocannabinol administered by oral gavage to male and female rats and mice in 14-day and 90-day subchronic studies. At the end of each study, all animals will be given gross and microscopic histopathologic evaluations. The results of the prechronic studies will be used by NTP to establish doses to be used in the chronic study.